The specific aim of this research is to test the hypothesis that the dominant white gene white gene (I) expresses itself in WL chickens by making the feather and choroid melanocytes more sensitive to a cytotoxic agent, possibly a compound produced by the melanocyte itself. Since this gene causes the feather melanocytes (and possibly the choroid melanocytes) in the WL chickens to die prematurely as compared to the melanocytes of the wild type Jungle Fowl (JF), the WL melanocytes may serve as a useful model for vitiligo. To test this hypothesis, the experimental design consists of four subdivisions. (I) Sensitivity differences of WL and JF melanocyte viability will be tested by the following experiments: (1) Location of the zone of cell death in the WL (I/I; I/i+) feathers; (2) the effect of unchanged media on the WL and JF in vitro melanocytes; (3) the effect on the in vitro melanocytes in the two genotypes by removing the feather piece from the petri dish; (4) the effect of L-dopa and tyrosine on the WL and JF in vitro melanocytes; and (5) the effect of 2-day conditioned media on the WL and JF in vitro melanocytes. (II) Experiments designed to gather evidence of melanin precursor compounds as a source of toxicity include: (1) The effect of tyrosine and L-dopa on WL and JF melanocytes in which melanogenesis has been stimulated by alpha-MSH; (2) the effect of alpha-MSH on viability of the WL and JF melanocytes in fresh and in unchanged media; and (3) gel chromatography to distinguish the active toxic fraction in WL conditioned media followed by high performance liquid chromatography if an active toxic fraction is found. (III) The experiments to check if 02- are involved in WL cell death would be to test the effect of the following enzymes and 02- scavengers (SOD, catalase, glutathione peroxidase, glutathione, cysteine, ascorbic acid, tocopherol, and melanin, itself) on the viability of the WL melanocytes. (IV) The experiments to see the effect of the dominant white gene on the eye, including a light- and electron-microscope study of the number of melanocytes in the regions of the eye, the physiological condition of these cells and their degree of melanin production. The effect of this same gene on feather tyrosinase and dopachrome conversion factor activity will be analyzed.